An internal combustion type pile driver comprising a cylinder, a ram adapted to slide within said cylinder, an anvil fitted into the bottom end of said cylinder and an air intake/exhaust port fixedly provided on said cylinder, has been heretofore known. However, the known internal combustion type pile drivers has fluctuations in the height of rise of the ram which determines the pile driving power, due to machining errors upon manufacture, and these fluctuations are hard to correct. Even if the height of rise of the ram is proper when the pile driver is new, after it is used for a certain period, wearing of the cylinder, ram and anvil becomes significant, and the pressure of the combustion gas is lowered due to leakage of air and the combustion gas. This results in an insufficient height of rise of the ram which leads a reduction of the pile driving power. In the known internal combustion type pile drivers, it is impossible to recover the original pile driving power for the used pile drivers.